U.S. Pat. No. 5,032,632 to Saxton (hereafter "SAXTON") discloses EVOH copolymer material having substantial viscosity stability during melt processing due to the incorporation of the following additives:
(a) metal salt of an aliphatic carboxylic acid having 3 to 9 carbon atoms; and PA1 (b) hindered phenolic antioxidant. PA1 1. anhydride functionalized polyolefin; and PA1 2. basic inorganic compound. PA1 1. EVOH copolymer; PA1 2. metal salt of aliphatic carboxylic acid having 3 to 9 carbon atoms (also hereafter referred to as "C3-C9 stabilizer"); and PA1 3. hindered phenolic antioxidant. PA1 1. EVOH polymer (base resin); PA1 2. anhydride functionalized polyolefin (resin toughener); PA1 3. basic inorganic compound (viscosity stabilizer to counteract any viscosity instability due to interaction between the EVOH and anhydride functionalized polyolefin resin toughener); PA1 4. metal salt of aliphatic carboxylic acid having 3 to 9 carbon atoms (also hereafter referred to as "C3-C9 STABILIZER"; this is part of the EVOH stabilizer system of SAXTON); PA1 5. hindered phenolic antioxidant (part of the EVOH stabilizer system of SAXTON). PA1 (a) about 40 to about 79 wt % ethylene comonomer, PA1 (b) about 0.5 to about 30 wt % carbon monoxide or sulfur dioxide, PA1 (c) about 20 to about 50 wt % unsaturated carboxylic acids or unsaturated derivatives of carboxylic acids other than anhydrides, and PA1 (d) about 0.01 to about 5 wt % of at least one comonomer containing pendant carboxylic acid anhydride functionality.
Applicant has found a way to toughen the compositions of SAXTON, while maintaining viscosity stability during melt processing.